PROPOSED PROGRAM In the proposed supplemental and renewal applications the investigators intend to conduct a longer term study of the neurologic function and developmental outcomes of a comparison of either total circulatory arrest or low-flow continuous cardiopulmonary bypass in infants with d-transposition of the great arteries requiring surgery within the first three months of life. In the current study they have studied the effects of the two intraoperative cardiopulmonary support methods on brain injury at the perioperative period and at age one year by looking at brain function using magnetic resonance imaging (MRI), electroencephalography (EEG), and neurologic examination. They are also studying development at one year of age using standardized psychometric testing. They now propose to extend the follow-up period to four years to enhance the predictive value of their neurologic and developmental assessments. The investigators will assess a primary outcome variable in the neurologic domain and a primary outcome variable in the developmental domain. The primary outcome variable of neurologic examination will result in an ordered classification of three categories of normal, minor, and major abnormalities. Secondary neurologic outcomes will be specific types of dysfunction, such as apraxia or cerebral palsy.The researchers will assess development using standardized measures of cognition, behavior, language, attention, and motor skills. The primary outcome variable for the developmental evaluation will be the intelligence quotient on the Wechsler Preschool and Primary Scale of Intelligence (WPPSI-R). Secondary outcome variables include measurements of behavior and performance in specific domains of speech and language, visual motor integration, attention, motor function, and temperament.